The present invention relates to a cover for vehicle wheels with light-metal rims during protracted transport such as is known, for example, from German publication DE 297 10 223 U1.
Light-metal rims, because of their greater permeability, as compared with steel rims covered by hubcaps, require a separate transport cover for protecting the brake disc against exterior rusting during protracted transport. Light-metal rims, moreover, usually contain a central centering bore which is designed identically at least in the case of all the rim types of a vehicle manufacturer which are provided for initial equipment. The outer orifice of this centering bore is closed when the vehicle is in the customer""s possession by a snapped-in lid which bears the vehicle manufacturer""s company logo. During transport, these snapped-in lids are removed and are placed as accessories in the vehicle interior.
In a wheel cover of the type referred to and known from DE 196 34 508 C1, the vehicle wheel is covered with a closed film moulding and fastened centrally to the vehicle wheel by fastening bosses which engage non-positively on the wheel screws/nuts or the corresponding countersinks. Although it is thereby possible for the cover to be mounted or demounted simply and quickly by hand, a secure hold of the cover on the vehicle wheel is not obtained in every instance of the many thousands which arise. In individual instances, therefore, the covers may come loose from the wheel during travel and/or in the event of a strong cross wind. It must also be remembered, in this connection, that, in individual instances, the wheel cover has to be removed in order to check and/or increase the tire air pressure. A cover according to the prior art, once it has fallen off or been deliberately removed, will therefore not be readily capable of being fastened securely to the vehicle wheel, because, when the film moulding is put in place for the first time, the bosses of the latter are often permanently deformed and, after the cover has been attached to a vehicle wheel for a second time, no longer make the secure non-positive connection to the screw-head countersinks which would be necessary per se. The secure fastening of a film moulding according to the prior art which is attached for the second time requires an additional aid, such as, for example, adhesive strips or the like. This is complicated and time-consuming.
In the wheel cover according to German Publication DE 297 10 223 U1 mentioned in the introduction, the film moulding has, in its center, a cylindrical holding connection piece which corresponds in diameter to the centering bore and which is inserted into the centering bore under prestress. A circumferentially extending row of catch noses on the circumference of the holding connection piece forms a positive connection with the rim hub. The shield part of the known wheel cover, lying radially between the wheel-screw ring and the rim flange, is virtually planar and is stiffened by a plurality of radially running reinforcing welts. So that the wheel cover fastened to the vehicle wheel can be released from the wheel again, as required, a grip depression is integrally formed in the film moulding on each of the two sides of one of the reinforcing welts. The known wheel cover can therefore be released from the wheel only by pulling at an eccentrically located point and along with considerable deformations of the transitional region from the shield part into the holding connection piece. The risk of tears and permanent deformations in the film moulding is, in this case, so great that it sometimes cannot be reused again. Should such a temporary removal of the known wheel cover, for example because of a loss of air pressure in the tire, be necessary during transport, and should the wheel cover be damaged at the same time, the brake disc of the respective wheel is unprotected for the remainder of the transport. A reliable reusability of the wheel cover is therefore necessary in functional terms.
US Pat. No. 5,039,172, likewise, shows a protective transport cover for light-metal rims of vehicles which is formed from a plastic film. In the near-center region of the wheel cover and at the outer edge, the film extends, in each case, in plane form and is provided there, on the wheel-facing side, with an annularly running pressure-sensitive adhesive strip with adhesive on two sides. In the cover part located radially between the center and the outer edge, the wheel cover has a highly wavy cross section as a result of a plurality of annular welts lying concentrically within one another. When the wheel cover is in the relaxed state, the wavy profile extends symmetrically on the near side and on the far side of the uniform plane of the center part and of the edge part. The purpose of this wavy cross-sectional configuration of the wheel cover is to make it possible, without great effort, to displace elastically the planar center part axially relative to the likewise plane edge part of the wheel cover and to adapt the center part to the rim. A precondition for using the wheel cover dealt with here is that, not only does the centering bore have a planar edge, but the rim flange also has an annularly running, likewise planar surface, in each case of a particular minimum width. However, planar surfaces of this type with a particular minimum width are ugly in configurational terms and are therefore not accepted by the customer. Consequently, as a rule, only surfaces curved to a greater or lesser extent are present on the rim, which, by virtue of their curvatures, can offer only relatively narrow adhesive surfaces for the film moulding, inherently rigid in the region of adhesion, and can therefore retain the wheel cover only with low forces. Apart from this, pressure-sensitive adhesives tend to creep when they undergo a long-lasting force action, as in the present case on account of the axially elastic deformation of the initially essentially planar wheel cover. It may therefore be that the point of adhesion of the wheel cover in the near-center region automatically comes loose from the rim over time. Another disadvantage of pressure-sensitive adhesives is that they generally become brittle and lose their adhesive force under the action of sunlight. When softeners counteracting embrittlement are added to the pressure-sensitive adhesives, there is the risk that adhesive residues will be left behind on the wheel rim after the removal of the wheel cover. These would have to be eliminated manually in a complicated way by the use of solvents. German publication DE 196 34 508 C1, assessed further above, refers to this problem in connection with a rim cover which it describes as being connected by a self-adhesive film. Apart from the cost disadvantage of pressure-sensitive adhesive strips and their attachment, the known protective transport cover to be glued to the rim therefore has many disadvantages in terms of use and, because of this, it is not considered advantageous by a person skilled in the art.
The cap for light-metal rims, which is shown in European publication EP 310 777 A1, is also designated as a wheel cover there, but it does not constitute a transport cover within the meaning of the present invention. On the contrary, the known cap is a decorative cap which is attached to the vehicle wheel during the normal use of the vehicle. The cap is intended to cover the near-center region of the light-metal rims, into the region of the wheel fastening screws, with a smooth surface and in an aesthetically pleasing way. Since the known decorative cap extends radially only as far as the wheel fastening screws, it cannot in any way assume the function of transport protection which is in question here. Moreover, the known decorative cap is designed as an injection moulding and not as a film moulding capable of being produced cost-effectively by a thermal deep-drawing method. In order to fasten the decorative cap to the light-metal rim, the decorative cap has, on the wheel-facing side, a plurality of axially projecting, radially resilient tongues which reach axially into the centering bore of the rim and bear under prestress on the inner surface of the bore. Integrally formed on the outside of the free ends of the elastic tongues are beads of triangular cross section which engage into a circumferential groove of trapezoidal cross section in the inner surface of the centering bore and thus positively secure the decorative cap axially on the light-metal rim. For simple demounting of the decorative cap, for example when a wheel change becomes necessary, deflecting bosses corresponding to one another are integrally formed on the outer edge of the decorative cap, on the one hand, and on the edge of the countersink receiving the decorative cap and located in the light-metal rim, on the other hand. By twisting the decorative cap, the deflecting bosses can be brought into engagement with one another, thus building up an axial force which is directed away from the wheel and by which the decorative cap can be released axially from the positive connection.
British publication GB 2 291 017 A, likewise, shows a decorative wheel cap. However, in the situation dealt with here, this cap can be used expediently only with steel rims on account of specific conditions. Conventionally, decorative wheel caps of steel rims cover the latter into the region of the rim flange and are clamped elastically to the outer circumference by way of the rim. However, the decorative wheel cap shown in the British publication mentioned here is of non-round design in the outer region for configurational reasons and also does not extend at all radially into the region of the rim flange. Since conventional outer clamping of the decorative wheel cap is ruled out as a result, the British publication mentioned here shows special measures for a near-center fixing of the decorative wheel cap. Specifically, four steel tongues project axially from the edge of the centering bore of the steel rim towards the outside of the wheel. The steel tongues together form a quadruply longitudinally slotted cylinder. Each of the tongues is reinforced at its free end in wall thickness both radially outwards and radially inwards. The tongues thus have holding extensions. Integrally formed in the center of the plastic decorative wheel cap produced as an injection moulding is an essentially cylindrical orifice. The inner surface of the orifice contains four shallow circumferential recesses which correspond to the four wheel-side steel tongues as xe2x80x9cnegativesxe2x80x9d to the shape of the latter. The known decorative wheel cap can therefore be slipped axially onto the wheel-side steel tongues. It is thereby centered on the vehicle wheel and secured fixedly in terms of rotation. Although the radially outer holding extensions at the ends of the steel tongues partially engage behind the edge of the cap-side orifice, they cannot offer sufficient safety against slipping off axially due to vibrations caused during driving. In order to improve the axial fixing of the known decorative wheel cap and to cover the remaining orifice, a decorative lid is provided. In a way similar to a bayonet fastening on the filler neck of a fuel tank, this lid can be fixed by an axial introduction movement and a subsequent rotational movement on the four steel tongues and their inner holding extensions. In order to handle the decorative lid, the latter is provided, likewise in the same way as a tank filler cap, on the free outer face with two grip depressions separated by a diametrically running bead.
British publication GB 2 229 975 A shows a wheel of the single type for use on doll prams, perambulators, shopping trolleys, office chairs or the like. The wheel, including the wheel tire, consists of a plurality of round plastic parts which can be plugged together axially and at the same time snapped permanently together with one another by elastic holding noses and catch depressions. The closing disc of the single wheel, located on the outside of the wheel, is an integral and supporting component of the wheel. There is no provision for demountability of the individual parts of the wheel on account of the inexpensive design of the single wheels.
The object of the present invention is to improve the rim cover so that it adheres to the vehicle wheel with a greater degree of fail safety and so that, even after temporary demounting, the rim cover can be attached to the wheel once again, just as securely, and adheres securely in place, as originally. As a result, the wheel cover can readily be reused after being in service.
According to the present invention a circumferential groove present in the inner surface of a wheel-side centering bore is utilized for the central fastening of the film moulding. By virtue of the axially running grooves integrally formed on the circumference of the holding connection piece, the holding connection piece can yield elastically in the radial direction when being inserted axially into the centering bore, or else when being pulled out. As a result, the application of the wheel cover, or its removal, becomes appreciably easier and even only slight damage to the catch noses or the holding connection piece is avoided. The deliberately small dimensioning of the end-face reinforcing flange also contributes to promoting a radial resilience of the holding connection piece. At the same time, however, a higher radial rigidity is achieved on the end face than at the region to be located axially towards the base of the holding connection piece. The high resilience in the shield part of the wheel cover, which is desirable for reasons of easy demountability and for the purpose of adaptability to different rim designs, is paired with an elastic prestress which ensures a secure hold on the rim. This is achieved by the cross-sectional shape of the shield part, which is inherently wavy, on the one hand, and is curved as a whole, on the other hand, together with the conical transition into the holding connection piece.